US5275670A - High temperature, oxidation resistant noble metal-Al alloy thermocouple - Google Patents
High temperature, oxidation resistant noble metal-Al alloy thermocouple Download PDFInfo
- Publication number
- US5275670A US5275670A US08/086,584 US8658493A US5275670A US 5275670 A US5275670 A US 5275670A US 8658493 A US8658493 A US 8658493A US 5275670 A US5275670 A US 5275670A
- Authority
- US
- United States
- Prior art keywords
- thermocouple
- leg
- noble metal
- alloy
- electropositive
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
- 229910000838 Al alloy Inorganic materials 0.000 title claims abstract description 48
- 230000003647 oxidation Effects 0.000 title abstract description 22
- 238000007254 oxidation reaction Methods 0.000 title abstract description 22
- 229910052703 rhodium Inorganic materials 0.000 claims abstract description 9
- 238000000576 coating method Methods 0.000 claims description 38
- 239000011248 coating agent Substances 0.000 claims description 27
- 229910000510 noble metal Inorganic materials 0.000 claims description 22
- 229910052697 platinum Inorganic materials 0.000 claims description 16
- 229910052741 iridium Inorganic materials 0.000 claims description 9
- 239000000758 substrate Substances 0.000 claims description 9
- 229910052763 palladium Inorganic materials 0.000 claims description 8
- 229910052737 gold Inorganic materials 0.000 claims description 6
- 229910052709 silver Inorganic materials 0.000 claims description 6
- 239000010948 rhodium Substances 0.000 abstract description 20
- 239000007789 gas Substances 0.000 abstract description 10
- 238000005259 measurement Methods 0.000 abstract description 7
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 abstract description 7
- 230000001590 oxidative effect Effects 0.000 abstract description 5
- 239000010970 precious metal Substances 0.000 abstract description 5
- 239000000470 constituent Substances 0.000 abstract description 4
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 51
- 229910052782 aluminium Inorganic materials 0.000 description 13
- 238000005269 aluminizing Methods 0.000 description 13
- 229910000951 Aluminide Inorganic materials 0.000 description 11
- 229910045601 alloy Inorganic materials 0.000 description 11
- 239000000956 alloy Substances 0.000 description 11
- 229910018404 Al2 O3 Inorganic materials 0.000 description 10
- 238000005229 chemical vapour deposition Methods 0.000 description 10
- 230000001681 protective effect Effects 0.000 description 9
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 8
- 238000009792 diffusion process Methods 0.000 description 8
- 229910052751 metal Inorganic materials 0.000 description 8
- 239000002184 metal Substances 0.000 description 7
- 239000010409 thin film Substances 0.000 description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 6
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 6
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 6
- 238000000034 method Methods 0.000 description 6
- 239000010408 film Substances 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- 238000011282 treatment Methods 0.000 description 5
- 229910001260 Pt alloy Inorganic materials 0.000 description 4
- 238000000137 annealing Methods 0.000 description 4
- 229910052786 argon Inorganic materials 0.000 description 4
- 230000008901 benefit Effects 0.000 description 4
- 239000010944 silver (metal) Substances 0.000 description 4
- 238000004544 sputter deposition Methods 0.000 description 4
- 229910000629 Rh alloy Inorganic materials 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 238000009529 body temperature measurement Methods 0.000 description 3
- 238000004518 low pressure chemical vapour deposition Methods 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 150000002739 metals Chemical class 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 229910000601 superalloy Inorganic materials 0.000 description 3
- 229910000881 Cu alloy Inorganic materials 0.000 description 2
- 229910017917 NH4 Cl Inorganic materials 0.000 description 2
- 229910000943 NiAl Inorganic materials 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- NPXOKRUENSOPAO-UHFFFAOYSA-N Raney nickel Chemical compound [Al].[Ni] NPXOKRUENSOPAO-UHFFFAOYSA-N 0.000 description 2
- 239000012190 activator Substances 0.000 description 2
- 238000000637 aluminium metallisation Methods 0.000 description 2
- 239000010953 base metal Substances 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 239000011162 core material Substances 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 230000008020 evaporation Effects 0.000 description 2
- 238000001704 evaporation Methods 0.000 description 2
- 239000010931 gold Substances 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 238000007654 immersion Methods 0.000 description 2
- 238000005304 joining Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 239000004576 sand Substances 0.000 description 2
- 239000000377 silicon dioxide Substances 0.000 description 2
- 229910002070 thin film alloy Inorganic materials 0.000 description 2
- 238000009834 vaporization Methods 0.000 description 2
- 230000008016 vaporization Effects 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910000570 Cupronickel Inorganic materials 0.000 description 1
- 229910001030 Iron–nickel alloy Inorganic materials 0.000 description 1
- 229910018967 Pt—Rh Inorganic materials 0.000 description 1
- 229910007277 Si3 N4 Inorganic materials 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- YOCUPQPZWBBYIX-UHFFFAOYSA-N copper nickel Chemical compound [Ni].[Cu] YOCUPQPZWBBYIX-UHFFFAOYSA-N 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000006378 damage Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- -1 e.g. Substances 0.000 description 1
- 230000008030 elimination Effects 0.000 description 1
- 238000003379 elimination reaction Methods 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 238000000265 homogenisation Methods 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 229910000765 intermetallic Inorganic materials 0.000 description 1
- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 description 1
- WABPQHHGFIMREM-UHFFFAOYSA-N lead(0) Chemical compound [Pb] WABPQHHGFIMREM-UHFFFAOYSA-N 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 238000005240 physical vapour deposition Methods 0.000 description 1
- UPIXZLGONUBZLK-UHFFFAOYSA-N platinum Chemical compound [Pt].[Pt] UPIXZLGONUBZLK-UHFFFAOYSA-N 0.000 description 1
- 230000002028 premature Effects 0.000 description 1
- 239000011819 refractory material Substances 0.000 description 1
- 230000000284 resting effect Effects 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N10/00—Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects
- H10N10/80—Constructional details
- H10N10/85—Thermoelectric active materials
- H10N10/851—Thermoelectric active materials comprising inorganic compositions
- H10N10/854—Thermoelectric active materials comprising inorganic compositions comprising only metals
Definitions
- thermocouples made of e.g., platinum (Pt), rhodium (Rh), palladium (Pd), iridium (Ir) , etc., and alloys thereof are known in the art.
- Pt-Pt13Rh the most widely used thermocouple for measurement of temperatures above 1000° C.
- one leg of the thermocouple is made of a wire or thin film of Pt and a second leg of the thermocouple is made of a wire or thin film of Pt13Rh (i.e., an alloy of platinum and rhodium containing 13 wt. % rhodium).
- FIG. 1 is a cross-sectional representation of the Pt leg wire of the Example below aluminized for four (4) hours at 1000° C. in accordance with the present invention.
- Inhomogeneity of a CVD coated or pack aluminized wire may cause diffusional instability. This could result in emf drift of the thermocouple, and is preferably minimized.
- annealing of the CVD coated or packed aluminized thermocouple leg element at about 1400° C. for about two hours in an inert atmosphere such as argon provides for homogenization of the outer aluminide coating, and effectively minimizes diffusional instability.
- thermocouple of the present invention may also take the form of a thermopile comprising a plurality of sensing junctions of the same material pairs in close proximity to each other and connected in series so as to multiply the emf output obtainable from a single sensing junction.
- the isothermal reference junctions are usually also in close proximity to each other to assure an equal temperature for each reference junction.
Landscapes
- Chemical & Material Sciences (AREA)
- Inorganic Chemistry (AREA)
- Measuring Temperature Or Quantity Of Heat (AREA)
Abstract
A thermocouple having an electropositive leg formed of a noble metal-Al alloy and an electronegative leg electrically joined at respective ends thereof to form a thermocouple junction. The thermocouple provides for accurate and reproducible measurement of high temperatures (600°-1300° C.) in inert, oxidizing, or reducing environments, gases or vacuum. Furthermore, the thermocouple circumvents the need for expensive, strategic precious metals such as rhodium as a constituent component. Selective oxidation of rhodium is also thereby precluded.
Description
The invention described herein was made by employees of the U.S. Government and may be manufactured and used by or for the Government, for governmental purposes without the payment of any royalties thereon or therefor.
1. Field of the Invention
This invention relates to a thermocouple adapted for accurate and reproducible measurement of high temperatures in inert, oxidizing or reducing environments, gases, or vacuum, and more particularly to a thermocouple leg comprising a noble metal-Al alloy.
2. Description of the Prior Art
High melting, noble metal thermocouples made of e.g., platinum (Pt), rhodium (Rh), palladium (Pd), iridium (Ir) , etc., and alloys thereof are known in the art. For example, the most widely used thermocouple for measurement of temperatures above 1000° C. is Pt-Pt13Rh, where one leg of the thermocouple is made of a wire or thin film of Pt and a second leg of the thermocouple is made of a wire or thin film of Pt13Rh (i.e., an alloy of platinum and rhodium containing 13 wt. % rhodium). The emf-temperature response of a Pt-Pt13Rh thermocouple, the basis of temperature measurement via thermocouples, is high (e.g., about 12.5 mv at 1200° C.) , and its oxidation resistance is good. The Pt-Pt13Rh thermocouple can be used with minimal drift (i.e., a change in emf with time due to any cause such as composition change, oxidation or chemical attack) up to 1500° C. Other precious metal elements, e.g., Pd and Ir, or alloys thereof with Pt are also useful thermocouples. Such thermocouples are not widely used because they are more susceptible to oxidation than Pt, and degrade by drift caused by selective oxidation.
On the other hand, Pt-modified pack aluminide coatings and the oxidation properties of these coatings in Pt-Al bulk alloys are known in the art. However, none of this technology concerns coating of Pt wires, making Pt-Al alloy wires, or using Pt-Al wires as thermocouple devices. The essence of the Pt-modified aluminide coating is that a thin layer (less than about 0.025 mm) of Pt is plated or CVD coated onto a nickel-base superalloy and then aluminized to form a Pt-Al rich outer layer in a NiAl coating. The Pt-Al phases are more diffusionally stable than NiAl, and serve as a long-term aluminum reservoir for protective Al2 O3 scale formation. Pt-Al oxidation studies have shown that about 5-10 a/o Al (atom %) is needed to form a protective Al2 O3 scale. Excellent oxidation resistance is obtained for these alloys.
A disadvantage of Pt-Pt13Rh as a thermocouple is its use of the strategic precious metal Rh. Rh is expensive and its availability is unreliable. Rh is also somewhat more prone to oxidation than Pt, so that alloys thereof suffer selective elimination of Rh resulting in a change in the emf of a Pt-Pt13Rh thermocouple over time (i.e., a temperature measurement inaccuracy). In reducing atmospheres, contact with any silica-containing material, e.g., silica-based refractories and SiC or Si3 N4 ceramics, can result in low melting Pt-Si compounds and destruction of the thermocouple.
The following patents relate to high temperature thermocouples, including Pt-Rh elements or analogous alloys which utilize rare and expensive metals or other metals.
U.S. Pat. No. 3,901,734 to Sibley et al relates to a thermocouple in which the positive element consists of an iron-nickel alloy and the negative element consists of a copper-nickel alloy. The compositions of these elements are such that inexpensive lead wires of copper, for example, may be used without any significant temperature error, where the thermocouple is used to monitor a temperature of about 1600° F. and the lead wire-thermocouple junction is at a temperature not exceeding about 400°-500° F. Particularly, the emf output of the Sibley et al thermocouple between 32° F. and about 500° F. is said to approach substantially zero when the compositions of the positive and negative thermoelements are properly selected.
U.S. Pat. No. 4,402,447 to Przybyszewski et al relates to a method for bonding a platinum base metal lead wire to a thin platinum alloy film (typically Pt or Pt10Rh) resting on a thin alumina insulating layer adhered to a metal substrate. Typically, the platinum alloy film forms an element of a thermocouple for measuring the surface temperature of a gas turbine airfoil.
U.S. Pat. No. 4,984,904 to Nakano et al relates to a platinum-platinum/rhodium alloy thermocouple housed in an immersion protection tube used to monitor the temperature of molten metal. The immersion protection tube formed of alumina-graphite is said to protect the thermocouple from high temperature exposure to a reducing atmosphere.
U.S. Pat. No. 5,043,023 to Bentley relates to a metal sheathed thermocouple cable comprising an oxidation-resistant nickel-based alloy. The thermocouple cable is said to have excellent thermoelectric and mechanical stability at high temperatures (beyond about 900° C.) , and is said to avoid premature failure due to oxidation that occurs in "bare-wire" thermocouples.
The following technical publications relate to platinum modified aluminide diffusion coatings.
M. R. Jackson et al, "The Aluminization of Platinum and Platinum-Coated IN-738", Metallurgical Transactions A, Vol. 8A, pages 1697-1707 (November 1977) relates to the chemistry and morphology of aluminide coatings formed on platinum and platinum-coated IN-738. These coatings are used to protect Ni-base superalloy gas turbine components from oxidation and hot corrosion attack.
J. S. Smith et al, "Platinum Modified Aluminides-Present Status", presented at the Gas Turbine and Aeroengine Congress and Expedition-Brussels, Belgium (Jun. 11-14, 1990) provides an overview of the development of platinum modified aluminide diffusion coatings used to impart oxidation and hot corrosion resistance to nickel-base superalloys. This paper discusses various coating morphologies and application of a low pressure chemical vapor deposition (low pressure CVD) process for production of platinum modified aluminide gas phase coatings on gas turbine components.
Accordingly, a first object of this invention is to provide a thermocouple for accurate and reproducible measurement of high temperatures (600°-1300° C.) in inert (e.g., Ar, He), oxidizing (e.g., air, O2, CO2, H2 O) or reducing (e.g., H2, CO, CH4) environments, gases, or vacuum.
A second object of this invention is to provide a thermocouple which exhibits low emf drift (defined as the change in emf with time due to any cause such as composition change, oxidation or chemical attack) for measurement of high temperatures in the above described environments.
A third object of this invention is to provide a thermocouple element for high temperature measurement which circumvents the need for expensive, strategic precious metals such as rhodium (Rh) as a constituent component. In this manner, selective oxidation of Rh is also precluded.
Other objects of this invention will become apparent in the following description and Example.
The present inventors have discovered that the above first and second objectives are achieved by a thermocouple comprising an electropositive leg and an electronegative leg, the electropositive leg and the electronegative leg being electrically joined at respective ends thereof to form a thermocouple junction, wherein the electropositive leg comprises a noble metal-Al alloy.
The present inventors have also discovered that the above third objective is achieved in accordance with a preferred embodiment of this invention where the electropositive leg comprises noble metal-Al alloy, and the noble metal is selected from the group consisting of Pt, Ir, Pd, Ag and Au. More preferably, the electropositive leg comprises a Pt-Al alloy. The electropositive leg and preferably the electronegative leg do not contain Rh.
Pt-Al alloys are known to form a protective Al2 O3 scale when exposed to an oxidative atmosphere. Ir is also known to form oxidation resistant alloys with aluminum, in much the same way as Pt-Al alloys are oxidation resistant. Similarly, we also expect Rh, Pd, Ag and Au to form oxidation resistant alloys with aluminum, but with decreasing temperature capability. Thus, Ir-Al or Pt-Ir-Al or Pd-Al alloy thermocouple legs, for example, are within the scope of this invention.
What was not hitherto recognized is that a significant emf exists between joined wires of a noble metal and a noble metal-Al alloy exposed to a high temperature differential, which allows these materials to advantageously be used as component parts of a novel type of thermocouple.
Also, we can envision a dilute Pt-Al alloy joined to a rich Pt-Al alloy that both form protective Al2 O3 scales, and are more diffusionally stable than just a pure Pt leg coupled to a Pt-Al leg. That is, the chemical driving force for diffusion would be reduced.
Thus, a first advantage of the thermocouple of the present invention over prior art thermocouples is that the expensive, strategic precious metal rhodium is not needed as a constituent component. Other benefits are that protective Al2 O3 scales form over the thermocouple leg, to thereby lessen any oxidation and vaporization of constituent components. This is especially useful when the thermocouple leg is in the form of a thin film, where vaporization and reaction with the underlying substrate is critical and may be alleviated by the protective Al2 O3 scales formed, for example, on Pt-Al alloys.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory but are not to be construed as being restrictive of the invention.
FIG. 1 is a cross-sectional representation of the Pt leg wire of the Example below aluminized for four (4) hours at 1000° C. in accordance with the present invention.
FIG. 2 is a diagram showing the method of Pt-Al thermocouple calibration of the Example below.
FIG. 3 is a graphical presentation showing emf output (mV) as function of temperature of the Pt/Pt-Al thermocouple having an electropositive Pt leg wire aluminized for four (4) hours at 1000° C. of the Example below. The superimposed circles are duplicate measurements giving nearly the same reproducible values.
The form of the thermocouple leg of the present invention is not particularly limited, and may comprise, for example, a thin wire or a thin film. A thermocouple leg wire in accordance with the present invention generally ranges from 0.25 to 2.0 mm in diameter, and Pt-Al coated wires in accordance with a preferred embodiment prepared, for example, by pack aluminizing or CVD (chemical vapor deposition) have a diameter of from 0.5 to 2.0 mm for optimum behavior. Thin film thermocouple elements in accordance with the present invention generally have a thickness in the range of from 0.02 to 0.20 mm. U.S. Pat. No. 4,402,447 to Przybyszewski et al describes the preparation of thin Pt/Rh alloy films and the joining of lead wires thereto for preparation of a high temperature thermocouple, and is incorporated herein by reference.
The noble metal for use in the present invention is selected from Pt, Ir, Rh, Pd, Ag, Au and combinations thereof. Pt and Ir are preferred. Pt is most preferred. When the thermocouple leg of the present invention does not contain Rh, the noble metal is selected from Pt, Ir, Pd, Ag, Au and combinations thereof.
The noble metal-Al alloy may take the form of a simple mixture, solid solution or intermetallic compound (e.g., a Ptx Aly compound) , or combinations thereof. The minimum Al content of the noble metal-Al alloy is about 5 atom %, and more preferably about 10 atom % for totally protective oxide formation, whereas the maximum Al content of the noble metal-Al alloy is about 67 atom % due to increasing brittleness with an increase in Al content. The Al content is preferably from 10 to 50 atom %.
As discussed above, the electropositive leg comprises a noble metal-Al alloy. The electronegative leg can comprise, for example, a noble metal or a noble metal-Al alloy, as long as the Al contents of the first and second legs are sufficiently different to produce an acceptable emf. In a preferred embodiment, both legs comprise a noble metal-Al alloy to thereby benefit from the oxidation resistance provided by the protective Al2 O3 scale. A preferred combination is 15-67 atom % Al and more preferably 40-60 atom % Al for the noble metal-Al alloy of the electropositive leg and 5-10 atom % Al for the noble metal-Al alloy of the electronegative leg. Particularly, this preferred combination allows a useful emf to be generated because of the substantial difference in Al contents, but still allows some formation of a protective Al2 O3 scale on the electronegative leg, while minimizing the potential for interdiffusion and emf drift.
The thermocouple legs comprising noble metal-Al alloys can be prepared, for example, by pack aluminizing, CVD coating, sputtering under a vacuum, or by pre-alloying in the master melt form of the wire or thin film production process. For example, pack aluminizing is readily accomplished by placing a noble metal wire in a bed of inert Al2 O3 sand containing about 2 wt. % Al powder and about 2 wt. % NH4 Cl activator at a temperature of about 1,000° C. The amount of aluminum incorporated into a coating of the noble metal wire increases with the pack aluminizing time. Pack aluminizing times of 1 to 4 hours are typical.
On the other hand, low pressure chemical vapor deposition may be employed to prepare a noble metal modified aluminide gas phase Al coating on a suitable substrate such as a Pt wire (or one of the other noble metals as defined above) followed by a post coating diffusion treatment (annealing) to form a noble metal - Al alloy. In the CVD coating process, HCl or HF is typically passed over a source of aluminum to generate an aluminizing gas. Advantageously, annealing can be conducted as part of the CVD cycle.
Alternatively, sputter coating of noble metal - Al alloys under vacuum is well adapted for preparing thin film alloy thermocouple elements for use in this invention. The thin film alloy thermocouple element might be deposited, for example, on a substrate such as a turbine airfoil test component as described by Przybyszewski et al, supra. In this case, the substrate does not participate in forming the noble metal - Al alloy.
J. S. Smith et al, and M. R. Jackson et al, supra. describe pack aluminizing and CVD coating; Przybyszewski et al, supra. describe sputtering under vacuum; and S. M. Sze, VLSI Technology, McGraw-Hill Book Company, pages 347-361 (1983) describes various techniques for Al metallization including physical vapor deposition, resistance heated evaporation, E-beam evaporation, inductive heating, sputtering and CVD. A post coating diffusion (annealing) treatment following Al metallization is typically carried out at a temperature of from 1000° to 1200° C. for a time of from 1 to 20 hrs. in argon or vacuum (i.e., non-oxidizing). All of the above techniques are readily adapted by one of ordinary skill in the art for preparing the noble metal-Al alloy for use in this invention.
The term "coating" is used herein to describe a noble-metal Al alloy formed in the outer portion of a substrate by pack aluminizing, as well as a noble metal-Al alloy formed, e.g., by Al deposition onto a substrate followed by post coating diffusion treatment.
Inhomogeneity of a CVD coated or pack aluminized wire may cause diffusional instability. This could result in emf drift of the thermocouple, and is preferably minimized. We have found that annealing of the CVD coated or packed aluminized thermocouple leg element at about 1400° C. for about two hours in an inert atmosphere such as argon provides for homogenization of the outer aluminide coating, and effectively minimizes diffusional instability.
When Al is supplied as a coating, we found successful operation of a Pt-Al thermocouple leg (following diffusion heat treatment) in the Pt2 Al3 to PtAl2 range. Thick PtAl2 coatings (0.18-0.25 mm) can cause cracking of a 1.0 mm diameter Pt wire if bent. We expect thin PtAl2 coatings of about 0.02-0.10 mm to be most useful. The amount of Pt consumed is generally on the order of 1/2 of the coating thickness. We expect noble metal-Al alloy coatings having a thickness of from 0.02 to 0.20 mm to be useful in this invention.
The preferred phases of the Pt-Al alloy are Pt2 Al3 or PtAl2 when the thermocouple is formed as a coating. However, as a bulk wire, the alloy may have to be PtAl or even less Al, and thus less emf, in order to maintain sufficient bulk ductility. Coated Pt wires thus offer a dual advantage of a ductile, low Al, core material combined with a thin high Al, high emf, Pt aluminide coating. For purposes of the aluminized wire, we optimized the thickness of the PtAl2 phase based on good emf response and suitable ductility. This was accomplished by aluminizing at 1,000° C. for 1, 4 and 16 hrs. as discussed in the Example below. We found that the 4 hr. treatment provided the best overall results.
In accordance with a preferred embodiment of this invention, the electropositive and electronegative legs comprising a Pt-Al alloy do not contain Rh. In this manner, selective oxidation and the expense of Rh is thereby precluded.
The electropositive leg and electronegative leg of the thermocouple of the present invention may be electrically joined at respective ends thereof to form a thermocouple junction, for example, by welding or by mechanical joining such as compression bonding. U.S. Pat. No. 4,415,758 to Lacoste et al describes a process for making a thermocouple junction between two small size thermocouple leg wires and is incorporated herein by reference. When used in the form of a thin film, the electropositive leg comprising a noble metal - Al alloy film and the electropositive leg comprising, for example, a Pt film may overlap to form a thermocouple junction as described by Przybyszewski et al., supra.
A thermocouple circuit in accordance with the present invention comprises an electropositive leg and an electronegative leg electrically joined together at one end (sensing junction) and terminated at their other end in such manner that the terminals (reference junction) are both at the same and known temperature (reference temperature). Connecting leads from the reference junction to a load resistance (e.g., an indicating meter such as a galvanometer or voltmeter, or the input impedance of other readout or signal-conditioning equipment) complete the thermocouple circuit. The connecting leads may be of copper alloy or some other metal different from the metals joined at the sensing junction. U.S. Pat. No. 3,372,062 to Zysk describes base metal leads for a noble metal thermocouple and is incorporated herein by reference. A current is caused to flow through the circuit whenever the sensing junction and the reference junction are at different temperatures. The reference junction may be held at a known constant temperature, or may be electrically compensated for variations from a preselected temperature.
The thermocouple of the present invention may also take the form of a thermopile comprising a plurality of sensing junctions of the same material pairs in close proximity to each other and connected in series so as to multiply the emf output obtainable from a single sensing junction. The isothermal reference junctions are usually also in close proximity to each other to assure an equal temperature for each reference junction.
For details regarding thermocouple circuits, reference may be made to Electronics Engineers' Handbook, 3rd Ed. McGraw-Hill Book Company, pages 10-30 to 10-32 (1989); Vassos et al, Analog and Digital Electronics for Scientists, pages 252-254, John Wiley & Sons, Inc. (1972); and A. J. Diefenderfer, Principles of Electronic Instrumentation, pages 82-84, W. B. Saunders Company (1972).
Details with respect to the present invention will be further described by way of the following Example to illustrate aspects of this invention, which Example is not intended to limit the scope or applicability of this invention.
Three (3) Pt-Al wires were prepared by aluminizing three (3) Pt wires for 1, 4 or 16 hrs. Aluminizing was accomplished by standard pack aluminizing at 1,000° C. in a bed of inert Al2 O3 sand containing 2 wt. % Al powder and 2 wt. % NH4 Cl activator. The aluminum pickup was monitored by Pt sheet specimens in the same packs, gaining 1.3 and 4.7 mg/cm2 for the 1 and 4 hr. treatments, respectively. The 16 hr. sheet sample spalled due to excessive aluminizing and brittleness. X-ray diffraction of the sheet samples revealed the presence of primarily Pt2 Al3 coating phases on all three wires. PtAl and the brittle PtAl2 phases were also present on the 1 and 16 hr. wires, respectively. One end of each wire was then torch welded to the ends of three Pt wires. All three resulting thermocouples were diffusion annealed at 1400° C. for 2 hrs. in argon to homogenize the outer aluminide coating. In reference to FIG. 1, the aluminide coating 1 over Pt core 2 of the 4 hr. wire had a thickness of about 0.075 mm. The Pt wires each had a diameter of 0.5 mm.
By reference to FIG. 2, the thermocouples 3 thus prepared were individually calibrated in a high temperature furnace 4 at temperatures up to 1400° C. against a standard Type R Pt-Pt13Rh couple 5 physically located less than 1 cm away. Measurements were taken by a voltmeter 6 (Doric 400A) in 100° C. degree increments. The lead wires 7 extending from the thermocouples were standard Type R thermocouple compensating copper alloy extension wires. Emfs of 0.62, 3.75 and 7.50 mV were obtained at 1400° C. for the 1, 4 and 16 hr. aluminized Pt-Al thermocouples, respectively. The 4 hr. thermocouple was aged at 1200° C. in air for 100 hrs. to check for drift, but no significant trend could be detected. A re-calibration run was conducted on the 4 hr. thermocouple, and the response thereof could be described by the equations:
emf=3.14E-5(T.sup.1.5741)
or
emf=-4.50E-11T.sup.3 +1.018E-6T.sup.2 +7.226E-4T-4.448E-2
The excellent fit of the first equation to the data is shown in FIG. 3. A similar fit was obtained with the second equation.
It should further be apparent to those skilled in the art that various changes in form and detail of the invention as shown and described above may be made. It is intended that such changes be included within the spirit and scope of the claims appended hereto.
Claims (20)
1. A thermocouple comprising an electropositive leg and an electronegative leg, said electropositive leg and said electronegative leg being electrically joined at respective ends thereof to form a thermocouple junction, wherein the electropositive leg comprises a noble metal-Al alloy.
2. The thermocouple of claim 1, wherein the noble metal is selected from the group consisting of Pt, Ir, Rh, Pd, Ag and Au.
3. The thermocouple of claim 1, wherein the noble metal is selected from the group consisting of Pt and Ir.
4. The thermocouple of claim 1, wherein the noble metal is Pt.
5. The thermocouple of claim 1, wherein the electronegative leg is made of Pt.
6. The thermocouple of claim 1, wherein the electronegative leg comprises a noble metal-Al alloy.
7. The thermocouple of claim 1, wherein the electropositive leg comprises a wire having a diameter of from 0.25 to 2.0 mm.
8. The thermocouple of claim 1, wherein the electropositive leg and the electronegative leg each comprise a film having a thickness of from 0.02 to 0.20 mm, which films overlap at respective ends thereof to form a thermocouple junction.
9. The thermocouple of claim 1, wherein the noble metal-Al alloy has an Al content of from 5 to 67 atom %.
10. The thermocouple of claim 1, wherein the electronegative leg comprises a noble metal-Al alloy having an Al content of from 5 to 10 atom % and the noble metal-Al alloy of the electropositive leg has an Al content of from 15 to 67 atom %.
11. The thermocouple of claim 1, wherein the electropositive leg is made of a noble metal-Al alloy.
12. The thermocouple of claim 1, wherein the electropositive leg comprises a substrate having a noble metal-Al alloy coating having a thickness of from 0.02 to 0.20 mm.
13. The thermocouple of claim 12, wherein the substrate is Pt, the noble metal of the noble metal-Al alloy coating is Pt, and the noble metal-Al alloy has an Al content of from 5 to 67 atom %.
14. A thermocouple comprising an electropositive leg and an electronegative leg, said electropositive leg and said electronegative leg being electrically joined at respective ends thereof to form a thermocouple junction, wherein the electropositive leg comprises a Pt wire having a Pt-Al alloy coating and the electronegative leg comprises a Pt wire or a Pt wire having a Pt-Al alloy coating.
15. The thermocouple of claim 14, wherein the Pt-Al alloy coating of the electropositive leg has an Al content of from 5 to 67 atom % and the electronegative leg comprises a Pt wire.
16. The thermocouple of claim 14, wherein the Pt-Al alloy coating of the electropositive leg has an Al content of from 15 to 67 atom %, and the electronegative leg comprises a Pt wire having a Pt-Al alloy coating having an Al content of from 5 to 10 atom %.
17. The thermocouple of claim 16, wherein the electropositive leg wire has a diameter of from 0.25 to 2.0 mm and the electronegative leg wire has a diameter of from 0.25 to 2.0 mm.
18. The thermocouple of claim 14, wherein the electropositive leg does not contain Rh.
19. The thermocouple of claim 14, wherein both the electropositve and electronegative legs do not contain Rh.
20. A thermocouple comprising an electropositive leg and an electronegative leg, said electropositive leg and said electronegative leg being electrically joined at respective ends thereof to form a thermocouple junction, wherein the electropositive leg comprises a noble metal - Al alloy, the noble metal is selected from the group consisting of Pt, Ir, Pd, Ag and Au, and the electropositive leg does not contain Rh.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/086,584 US5275670A (en) | 1993-07-06 | 1993-07-06 | High temperature, oxidation resistant noble metal-Al alloy thermocouple |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/086,584 US5275670A (en) | 1993-07-06 | 1993-07-06 | High temperature, oxidation resistant noble metal-Al alloy thermocouple |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US5275670A true US5275670A (en) | 1994-01-04 |
Family
ID=22199534
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US08/086,584 Expired - Fee Related US5275670A (en) | 1993-07-06 | 1993-07-06 | High temperature, oxidation resistant noble metal-Al alloy thermocouple |
Country Status (1)
| Country | Link |
|---|---|
| US (1) | US5275670A (en) |
Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5560478A (en) * | 1992-11-19 | 1996-10-01 | Moore; Lovell C. | Ready-to-use copper pipe nipple apparatus |
| US6850859B1 (en) | 2003-12-03 | 2005-02-01 | Watlow Electric Manufacturing Company | Sensor drift compensation by lot |
| US20050129091A1 (en) * | 2003-12-16 | 2005-06-16 | Habboosh Samir W. | Extended temperature range EMF device |
| US20050145960A1 (en) * | 2003-12-16 | 2005-07-07 | Habboosh Samir W. | EMF sensor with protective sheath |
| US20060045164A1 (en) * | 2004-08-31 | 2006-03-02 | Schuh William C | System and method of compensation for device mounting and thermal transfer error |
| US20110121713A1 (en) * | 2009-11-24 | 2011-05-26 | Federal-Mogul Ignition Company | Spark plug with platinum-based electrode material |
| EP2617860A1 (en) * | 2010-09-09 | 2013-07-24 | National Institute for Materials Science | Alloy material for high temperature service having excellent oxidation resistance properties, and process for production thereof |
| US20130243036A1 (en) * | 2010-03-31 | 2013-09-19 | Cambridge Enterprise Limited | Thermocouple apparatus and method |
| CN107805804A (en) * | 2017-10-09 | 2018-03-16 | 国网江西省电力公司电力科学研究院 | A kind of preparation method of Pt Al high-temperature oxidation resistant coatings |
| US10161807B2 (en) | 2016-09-23 | 2018-12-25 | Rolls-Royce Corporation | Thin-film thermocouple for measuring the temperature of a ceramic matrix composite (CMC) component |
| CN113174568A (en) * | 2021-04-20 | 2021-07-27 | 中国航发北京航空材料研究院 | Method for preparing indium tin oxide-indium oxide film thermocouple with crystal face preferred orientation |
| US12181351B2 (en) | 2018-02-28 | 2024-12-31 | Arthur Beckman | Thermopile assembly providing a massive electrical series of wire thermocouple elements |
Citations (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1789733A (en) * | 1924-09-08 | 1931-01-20 | Firm W C Heraeus Gmbh | Thermoelectric generator |
| US2335707A (en) * | 1941-06-21 | 1943-11-30 | American Platinum Works | Thermocouple wire |
| US2406172A (en) * | 1942-02-07 | 1946-08-20 | Baker And Co Inc | Platinum or allied metals, or their alloys, and articles made therefrom |
| US2846493A (en) * | 1955-11-30 | 1958-08-05 | Rca Corp | Nu-type thermoelectric devices |
| US2846494A (en) * | 1955-11-30 | 1958-08-05 | Rca Corp | Thermoelectric devices |
| US3066177A (en) * | 1960-02-25 | 1962-11-27 | Engelhard Ind Inc | Thermocouple |
| US3372062A (en) * | 1964-06-22 | 1968-03-05 | Engelhard Ind Inc | Noble metal thermocouple having base metal leads |
| US3901734A (en) * | 1973-08-23 | 1975-08-26 | Hoskins Manufacturing Co | Thermocouple |
| US4110124A (en) * | 1975-09-22 | 1978-08-29 | Engelhard Minerals & Chemicals Corporation | Thick film thermocouples |
| US4402447A (en) * | 1980-12-04 | 1983-09-06 | The United States Of America As Represented By The Administrator Of National Aeronautics And Space Administration | Joining lead wires to thin platinum alloy films |
| US4415758A (en) * | 1979-11-07 | 1983-11-15 | Commissariat A L'energie Atomique | Process for making a joint between two metal wires and a differential thermocouple |
| US4984904A (en) * | 1987-12-24 | 1991-01-15 | Kawaso Electric Industrial Co., Ltd. | Apparatus for continuously measuring temperature of molten metal and method for making same |
| US5043023A (en) * | 1986-09-08 | 1991-08-27 | Commonwealth Scientific And Industrial Research Organization | Stable metal-sheathed thermocouple cable |
-
1993
- 1993-07-06 US US08/086,584 patent/US5275670A/en not_active Expired - Fee Related
Patent Citations (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1789733A (en) * | 1924-09-08 | 1931-01-20 | Firm W C Heraeus Gmbh | Thermoelectric generator |
| US2335707A (en) * | 1941-06-21 | 1943-11-30 | American Platinum Works | Thermocouple wire |
| US2406172A (en) * | 1942-02-07 | 1946-08-20 | Baker And Co Inc | Platinum or allied metals, or their alloys, and articles made therefrom |
| US2846493A (en) * | 1955-11-30 | 1958-08-05 | Rca Corp | Nu-type thermoelectric devices |
| US2846494A (en) * | 1955-11-30 | 1958-08-05 | Rca Corp | Thermoelectric devices |
| US3066177A (en) * | 1960-02-25 | 1962-11-27 | Engelhard Ind Inc | Thermocouple |
| US3372062A (en) * | 1964-06-22 | 1968-03-05 | Engelhard Ind Inc | Noble metal thermocouple having base metal leads |
| US3901734A (en) * | 1973-08-23 | 1975-08-26 | Hoskins Manufacturing Co | Thermocouple |
| US4110124A (en) * | 1975-09-22 | 1978-08-29 | Engelhard Minerals & Chemicals Corporation | Thick film thermocouples |
| US4415758A (en) * | 1979-11-07 | 1983-11-15 | Commissariat A L'energie Atomique | Process for making a joint between two metal wires and a differential thermocouple |
| US4402447A (en) * | 1980-12-04 | 1983-09-06 | The United States Of America As Represented By The Administrator Of National Aeronautics And Space Administration | Joining lead wires to thin platinum alloy films |
| US5043023A (en) * | 1986-09-08 | 1991-08-27 | Commonwealth Scientific And Industrial Research Organization | Stable metal-sheathed thermocouple cable |
| US4984904A (en) * | 1987-12-24 | 1991-01-15 | Kawaso Electric Industrial Co., Ltd. | Apparatus for continuously measuring temperature of molten metal and method for making same |
Non-Patent Citations (12)
| Title |
|---|
| "Platinum Modified Aluminides--Present Status", presented at the Gas Turbine and Aeroengine Congress and Expedition--Brussels, Belgium, J. S. Smith et al, Jun. 11-14, 1990, pp. 1-10. |
| Diefenderfer, A. James, Principles of Electronic Instrumentation , 1972, pp. 82 84. * |
| Diefenderfer, A. James, Principles of Electronic Instrumentation, 1972, pp. 82-84. |
| Fink, Donald G. and Donald Christiansen, eds., Electronics Engineers Handbook , 1989, pp. 10 30 10 32. * |
| Fink, Donald G. and Donald Christiansen, eds., Electronics Engineers Handbook, 1989, pp. 10-30-10-32. |
| Metallurgical Transactions A , vol. 8A, pp. 1697 1707 (Nov. 1977), MR. Jackson et al, The Aluminization of Platinum and Platinum Coated IN 738 . * |
| Metallurgical Transactions A, vol. 8A, pp. 1697-1707 (Nov. 1977), MR. Jackson et al, "The Aluminization of Platinum and Platinum Coated IN-738". |
| Platinum Modified Aluminides Present Status , presented at the Gas Turbine and Aeroengine Congress and Expedition Brussels, Belgium, J. S. Smith et al, Jun. 11 14, 1990, pp. 1 10. * |
| Sze, S.M., ed., VLSI Technology , pp. 347 361, 1983. * |
| Sze, S.M., ed., VLSI Technology, pp. 347-361, 1983. |
| Vassos, Basil H. and Galen W. Ewing, Analog and Digital Electronics for Scientists , 1972, pp. 252 254. * |
| Vassos, Basil H. and Galen W. Ewing, Analog and Digital Electronics for Scientists, 1972, pp. 252-254. |
Cited By (23)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5560478A (en) * | 1992-11-19 | 1996-10-01 | Moore; Lovell C. | Ready-to-use copper pipe nipple apparatus |
| US6850859B1 (en) | 2003-12-03 | 2005-02-01 | Watlow Electric Manufacturing Company | Sensor drift compensation by lot |
| US20050129091A1 (en) * | 2003-12-16 | 2005-06-16 | Habboosh Samir W. | Extended temperature range EMF device |
| US20050145960A1 (en) * | 2003-12-16 | 2005-07-07 | Habboosh Samir W. | EMF sensor with protective sheath |
| US7131768B2 (en) | 2003-12-16 | 2006-11-07 | Harco Laboratories, Inc. | Extended temperature range EMF device |
| US7611280B2 (en) | 2003-12-16 | 2009-11-03 | Harco Laboratories, Inc. | EMF sensor with protective sheath |
| US20060045164A1 (en) * | 2004-08-31 | 2006-03-02 | Schuh William C | System and method of compensation for device mounting and thermal transfer error |
| US7447607B2 (en) | 2004-08-31 | 2008-11-04 | Watow Electric Manufacturing | System and method of compensation for device mounting and thermal transfer error |
| US20090024348A1 (en) * | 2004-08-31 | 2009-01-22 | Watlow Electric Manufacturing Company | System and method of compensating for device mounting and thermal transfer errors |
| US8311763B2 (en) | 2004-08-31 | 2012-11-13 | Watlow Electric Manufacturing Company | System and method of compensating for device mounting and thermal transfer errors |
| US8274204B2 (en) | 2009-11-24 | 2012-09-25 | Federal-Mogul Ignition Company | Spark plug with platinum-based electrode material |
| US20110121713A1 (en) * | 2009-11-24 | 2011-05-26 | Federal-Mogul Ignition Company | Spark plug with platinum-based electrode material |
| US20130243036A1 (en) * | 2010-03-31 | 2013-09-19 | Cambridge Enterprise Limited | Thermocouple apparatus and method |
| US9702764B2 (en) * | 2010-03-31 | 2017-07-11 | Cambridge Enterprise Limited | Thermocouple apparatus and method |
| US10168228B2 (en) | 2010-03-31 | 2019-01-01 | Cambridge Enterprise Limited | Thermocouple apparatus and method |
| EP2617860A1 (en) * | 2010-09-09 | 2013-07-24 | National Institute for Materials Science | Alloy material for high temperature service having excellent oxidation resistance properties, and process for production thereof |
| EP2617860A4 (en) * | 2010-09-09 | 2014-06-25 | Nat Inst For Materials Science | ALLOY MATERIAL FOR USE AT HIGH TEMPERATURE, WHICH HAS EXCELLENT OXIDATION RESISTANCE PROPERTIES, AND PROCESS FOR PRODUCING THE SAME |
| US10161807B2 (en) | 2016-09-23 | 2018-12-25 | Rolls-Royce Corporation | Thin-film thermocouple for measuring the temperature of a ceramic matrix composite (CMC) component |
| CN107805804A (en) * | 2017-10-09 | 2018-03-16 | 国网江西省电力公司电力科学研究院 | A kind of preparation method of Pt Al high-temperature oxidation resistant coatings |
| CN107805804B (en) * | 2017-10-09 | 2019-01-11 | 国网江西省电力公司电力科学研究院 | A kind of preparation method of Pt-Al high-temperature oxidation resistant coating |
| US12181351B2 (en) | 2018-02-28 | 2024-12-31 | Arthur Beckman | Thermopile assembly providing a massive electrical series of wire thermocouple elements |
| CN113174568A (en) * | 2021-04-20 | 2021-07-27 | 中国航发北京航空材料研究院 | Method for preparing indium tin oxide-indium oxide film thermocouple with crystal face preferred orientation |
| CN113174568B (en) * | 2021-04-20 | 2022-11-22 | 中国航发北京航空材料研究院 | Method for preparing indium tin oxide-indium oxide film thermocouple with crystal face preferred orientation |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US5275670A (en) | High temperature, oxidation resistant noble metal-Al alloy thermocouple | |
| US8334056B2 (en) | High-temperature coatings with Pt metal modified γ-Ni + γ′-Ni3Al alloy compositions | |
| Kreider et al. | Platinum/palladium thin-film thermocouples for temperature measurements on silicon wafers | |
| US20110023619A1 (en) | Thin film ceramic thermocouples | |
| US5010316A (en) | Thermocouples of enhanced stability | |
| US4018569A (en) | Metal of improved environmental resistance | |
| JPH01501108A (en) | stable metal sheathed thermocouple cable | |
| US4834807A (en) | Thermocouples of enhanced stability | |
| Brown | The Relationship of Heat Treatment to the Corrosion Resistance of Stainless Alloys | |
| Kreider | Sputtered high temperature thin film thermocouples | |
| JPH02503576A (en) | Coated near-α titanium product | |
| Pennisi et al. | Improved plasma-sprayed Ni-Co-Cr-Al-Y and Co-Cr-Al-Y coatings for aircraft gas turbine applications | |
| CA1238116A (en) | Stable high temperature cables and devices made therefrom | |
| Deodeshmukh et al. | Effects of Platinum on the Hot Corrosion Behavior of Hf-Modified γ′-Ni 3 Al+ γ-Ni-Based Alloys | |
| AU610527B2 (en) | Thermocouples of enhanced stability | |
| Crookes | The volatility of metals of the platinum group | |
| Smith et al. | High temperature resistivity and thermo-EMF of RuAl | |
| US3442720A (en) | Method of forming ti-modified silicide coatings on cb-base substrates and resulting articles | |
| JPH04228530A (en) | Iridium-silicon alloy | |
| Mu et al. | The development and performance of novel Pt+ Hf-modified γ′-Ni3Al+ γ-Ni bond coatings for advanced thermal barrier coatings systems | |
| WO1990009682A1 (en) | Pyrometric thermoelectric sensor | |
| Natesan et al. | Electrically insulating coatings for V-Li self-cooled blanket in a fusion system | |
| EP0161986A2 (en) | Stable high temperature cables and devices made therefrom | |
| JPS5951323A (en) | Thermistor | |
| Vlakhov et al. | Superconducting properties of CVD tantalum films |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| AS | Assignment |
Owner name: UNITED STATES OF AMERICA, THE, AS REPRESENTED BY T Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:SMIALEK, JAMES L.;GEDWILL, MICHAEL A.;REEL/FRAME:006673/0327 Effective date: 19930625 |
|
| REMI | Maintenance fee reminder mailed | ||
| FPAY | Fee payment |
Year of fee payment: 4 |
|
| SULP | Surcharge for late payment | ||
| FPAY | Fee payment |
Year of fee payment: 8 |
|
| REMI | Maintenance fee reminder mailed | ||
| LAPS | Lapse for failure to pay maintenance fees | ||
| STCH | Information on status: patent discontinuation |
Free format text: PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362 |
|
| FP | Lapsed due to failure to pay maintenance fee |
Effective date: 20060104 |